Door alarm



Feb. 4, 1969 M. L. CAMPBELL 3,425,386

DOOR ALARM Filed Nov. 30. 1966 INVENTOR Q2 Max L. Campbell BY f United States Patent 4 Claims ABSTRACT OF THE DISCLOSURE A percussion cap firing mechanism is mounted on the hinge of a door such that the mechanism will be tripped upon opening of the door to provide an audible alarm.

The primary object of this invention is to provide an alarm which is operated by the opening of a door and which, upon actuation, delivers a loud, explosive report. The entry of burglars or other unauthorized perons is thus signalled to expose the presence of such person and, additionally, the report serves to startle the intruder and hopefully encourage his retreat.

As a corollary to the foregoing object, it is also an important aim of the instant invention to provide such an alarm which is solely mechanical in operation, easily and rapidly installed on conventional doors in a location concealed from an intruder, foolproof in operation and which may be reset and rearmed by perons who are not especially skilled in the handling of detonation devices.

In the drawing:

FIGURE 1 is a plan view of the firing mechanism showing the same cocked and mounted on a door hinge;

FIG. 2 is a view similar to FIG. 1 showing the mechanism prior to cooking or after firing;

FIG. 3 is a front elevational view of the structure shown in FIG. 2;

FIG. 4 is a fragmentary, side elevational view of the structure shown in FIGS. 2 and 3, the hinge pin being raised to illustrate the manner of installation;

FIG. 5 is a sectional view taken along line 55 of FIG. 1, the coil spring being removed for clarity; and

FIG. 6 is a detail of the percussion cap and anvil.

The edge of a door 10 is shown supported by a portion of a doorframe 12 having the usual facing or rail 14. The doorstop is illustrated at 16, and a corner stud 18 is shown in conjunction with a wall 20 terminating at frame 12. The foregoing structure is representative of a conventional door installation wherein a hinge assembly 22 is utilized to support the door for swinging movement between open and closed positions. Assembly 22 includes hinge barrel components 24 and 26 secured to door 10 and frame 12, respectively, and a vertical hinge pin 28.

A firing mechanism is broadly denoted 30 and includes an upper arm 32 and a lower arm 34 extending generally horizontally and radially from a tubular bolt 36. Hinge pin 28 is inserted into bolt 36, as illustrated in FIG. 4, to mount mechanism 30 on hinge assembly 22. This is effected by removing pin 28 from barrel components 24 and 26 and then reinsertiug pin 28 after passing the same through bolt 36, whereupon the latter remains telescoped over pin 28 between the top of barrel 24 and the head of the hinge pin.

Bolt 36 has a head 38 which forms the hub of the upper arm 32, the latter thus being integral with the bolt. The lower arm 34 has a hub 40 provided with an internal bore of slightly larger diameter than the outside diameter of bolt 36, permitting free turning of arm 34 on the bolt.

The outer extremity of upper arm 32 has a lateral projection 42 provided with an :anvil 44 in the form of a cylindrical protuberance upon which a percussion cap 46 is seated. FIGURE 6 shows cap 46 in section and reveals the explosive charge 48 which is confined between anvil 44 and the base portion of cap 46.

The lower arm 34 is provided with a hammer 50 at its outer extremity in the form of a lateral projection which extends toward anvil 44. A coil spring 52 is telescoped over the lower portion of bolt 36 and is held between the underside of the hub 40 of arm 34 and a knurled take-up nut 54 threaded on the lower end of bolt 36. Spring 52 has outwardly extending terminal legs 56 and 58 which are joined to arms 34 and 32 respectively.

In FIG. 5 it may be seen that a nib 60 projects downwardly from the underside of bolt head 38, nib 60 being shown received in a notch 62 in the upper surface of hub 40. A portion of hub 40 from a point adjacent notch 62 to arm 34 is relieved at 64.

A pair of adjustable stops 66 and 68 are threaded into arms 32 and 34 respectively as illustrated and have feet which engage, or nearly engage, door 10 and frame rail 14 when mechanism 30 is installed on hinge pin 28 as illustrated in FIG. 1. This is the cocked position of the mechanism, it being appreciated from FIG. 5 that the arms 32 and 34 are locked against movement by the seating of nib 60 in notch 62. Nib 60 is held in notch 62 by the bias of spring 52, the latter being compressed between hub 40 and nut 54. As door 10 is swung open by an intruder, the force of the door against stop 66 shifts arm 32 toward arm 34 and, in so doing, momentarily separates head 38 and hub 40 by shifting the latter against the action of spring 52. It is apparent that the combined effect is to unseat nib 60 from notch 62, unlocking the arms and permitting spring 52 to drive the arms toward one another. This causes impactive interengagement of hammer 50 and cap 46, thereby detonating the charge 48 and signaling the presence of the intruder. The relief 64 allows the arms to move under the action of spring 52 without binding against nib 60 so that the striking force of hammer 50 will not be impaired by excessive friction between the moving parts.

Recocking and reloading of mechanism 30 is readily effected by manually grasping arms 32 and 34 and separating the same until nib 60 falls into notch 62. An unexpended cap 46 is then slipped over anvil 44 and the device is ready for reuse. During times when it is desired that the door 10 be freely openable without sounding an alarm, arms 32 and 34 may be manually shifted toward one another, holding against spring 52, and placed at rest as illustrated in FIGS. 2-4 with an unexpended cap on anvil 44.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. An alarm comprising:

a support;

a first and a second element;

structure mounting said elements on the support for relative movement toward and away from each other;

a lock between the elements normally maintaining the same apart;

an anvil on said first element having means for receiving a percussion cap;

a hammer disposed on said second element to strike the cap and fire the same when the elements move relatively toward each other,

said support having means for mounting the same adjacent a door with one of the elements in the path of travel of the door when the latter is opened,

said lock being releasable upon movement of said one element by the door; and

means interconnecting the elements for snapping the hammer against the cap upon release of said lock,

each of said elements including an arm extending from said support,

said one element being provided with a stop extending from the arm thereof for engagement with said door when said support is mounted adjacent the door,

the other of said elements being provided with a stop extending from the arm thereof and engageable with a doorframe for said door when said support is mounted adjacent the door.

2. An alarm comprising:

a support;

a first and a second element;

structure mounting said elements on the support for relative movement toward and away from each other;

a lock between the elements normally maintaining the same apart;

an anvil on said first element having means for receiving a percussion cap;

a hammer disposed on said second element to strike the cap and fire the same when the elements move relatively toward each other,

said support having means for mounting the same adjacent a door with one of the elements in the path of travel of the door when the latter is opened,

said lock being releasable upon movement of said one element by the door; and

means interconnecting the elements for snapping the hammer against the cap upon release of said lock,

said support including a hinge assembly for mounting said door in a doorframe.

3. The invention of claim 2,

said assembly having a hinge pin,

said structure including a tubular member telescoped over said pin.

4. The invention of claim 3,

each of said elements including an arm,

said arms being juxtaposed and carried by said member, and being independently rotatable about the axis thereof,

said hammer snapping means including a coil spring telescoped over a portion of said member and having a pair of terminal legs engaging respective arms,

said lock comprising a nib on one of said arms receivable within a notch on the other of said arms, and take-up means on the member clamping the spring between the take-up means and the arms to bias the latter toward each other.

References Cited UNITED STATES PATENTS 118,345 8/1871 Coulston 11683 394,707 12/1888 Mikich 11683 701,753 6/1902 Moody 116-87 713,965 11/1902 Conklin 116-83 874,202 12/1907 Humason 116-87 1,392,326 10/1921 Hardwick 11687 LOUIS J. CAPOZI, Primary Examiner.

US. Cl. X.R. 

